ISIS Electrical Engineering Group Mike Glover

ISIS Electrical Engineering Group Structure

ISIS Electrical Engineering Group Structure

Areas of Responsibility ISIS Synchrotron Power Supplies ISIS Extracted Proton Beam Line Power Supplies ISIS Neutron Beam Line Chopper Power Supplies Electrical Engineering of ISIS Control Systems for: Vacuum Systems Water Plant Systems Electrical Engineering of Neutron Instrument Beam Line Installations

ISIS Synchrotron Power Supplies Main Magnet “White Circuit” 14.4kV 650ADC 400AAC Injection & Extraction Septum 5kA & 10kA 50V DC Injection Dipole 50Hz 13kA 500µS Flat Top 100µS Rise Time Ring Steering & Trim Quadrupoles 4 Quadrant 150kA/S 250 Amp Programmable Fast Extraction Kicker Magnets 50Hz 40kV 5kA 500nS Flat Top 80nS Rise Time

Injection Septum Deflects the injected beam into the aperture of the injection dipole magnet and onto the foil 200kW 5000 Amps 40V 1416 Transistor Regulator 100ppm stability

Extraction Septum Magnet Bend 21º 10,000 Amps 50V 11kV Supply Rectifier Transistor Regulator 4 Sets of 24 Transistor Banks 2304 Transistors

Extraction of Beam At Extraction Protons Circulating at 800 MeV Two bunches with 200 ns gap Extraction System 3 fast kicker magnets deflect the beam into … a septum magnet which lifts it into the EPB Kickers need to be fast to avoid beam loss Go from zero to full field between passage of bunches

Extraction Details Kickers 3 units give 15 mr kick Rise Time 80 nS Flat Top 500 nS 5000A 40kV 50Hz pulsed Septum ~ 8 m downstream 8 Turn, 8900 A DC 1.8 m long (21 degrees) Lifts beam out of machine

ESSO Ring Vacuum PLC Control System

ESSO Neutron Beam Line Installations Complete electrical design Electrical Supply Detector Cabling Chopper Cabling Vacuum System Controls Several kilometres of cabling per beam line

Power Systems and the ISIS Synchrotron Andrew Kimber

Outline Main magnet systems MM Power Supply and the White Circuit Capacitor bank replacement UPS Replacement 1MJ Storage Choke Summary

Magnet systems Main Magnets 10 Bending Dipoles 10 Singlet Quadrupoles 10 Focussing Doublet Quadrupoles. Corresponds to 10 superperiods

Main magnet power supply

Main magnet power supply For successful acceleration the same magnetic field is required in all the main magnets Main Magnets per super period: 1 Dipole 1 Singlet Quadrupole 1 Doublet Quadrupole How do we connect these? One power supply per super period Main Magnet System operates at 14.4kV Current changes from 250A to 1050 Amps Peak Power = 15.1 MVA For 10 super periods the Peak Power Required = 151 MVA Excessive Power Required !

Main magnet power supply Magnets have Inductance Inductance can store energy E = ½ LI2 Capacitors also store energy E = ½ CV2 Resonate the stored energy between Inductor and capacitor: With no losses in the system the impedances of the Inductance and the Capacitance would be identical and energy would be transferred with an alternating current between them and at a resonant frequency. Inductance reactance XL = Capacitive reactance XC ωL = 1/ωC ω = 2π f Resonant Frequency f = 1/(2π√LC )

Main magnet power supply Normal Temperature Magnets have Resistance Capacitors have losses Cables have losses If the losses << Inductance we have a high ‘Q’ oscillating system. We just require to supply make up power for the resistive and AC losses in the Magnets, Cables and Connectors.

The White Circuit WHITE CIRCUIT M G White, Princeton (1956) CERN Symposium Oscillate the magnet cell using capacitors and choke. Connect all the magnets together electrically and same current flows through each magnet. Permit DC bias current through split choke secondary winding Power required is to make up for the resistive losses in the copper, ac losses in the magnets and power supply losses. IM = IDC – IAC cos ω t Total of 1.75MW (150MVA peak for non resonant circuit)

The White Circuit

Main magnet power supply Replace capacitor bank with smaller more efficient units. Replace the Motor Alternator Set with a UPS System Replace the Choke. Split the Choke into 10 separate units and build spare as well. PROGRESS TO DATE Capacitor bank replaced (2002) UPS system currently on order. Build a scale model to prove theory of split choke. Scale model chokes currently being ordered.

Old Capacitor Banks

New Capacitor Banks Replaced in 2002 Smaller units, space used for 1 old bank is now used for 5.

Motor Alternator Set

Previous Motor Alternator Set Brentford Excitation PSU 12KVA Mains supply 5KV single phase 3.6KV single phase Storage choke and main magnets DC Motor Alternator shaft transformer Phase locked to ISIS 50Hz reference signal Electromechanical Single phase output 2 phases connected line to line and 1 disconnected Alternator phase locked to ISIS 50Hz reference 100Hz induced harmonic between raw mains and reference signal

Current Motor Alternator Set Brentford Excitation PSU 12KVA Mains supply Phase locked to ISIS 50Hz reference signal UPS 5KV single phase 3.6KV single phase Storage choke and main magnets DC Motor Alternator shaft transformer Phase locked to ISIS 50Hz reference signal Alternator and UPS phase locked to ISIS 50Hz reference Factor of 2 improvement in AC stability

New UPS system Motor alternator set replaced with 4 300KVA units three phase 720V single phase 3.6KV single phase Storage choke and main magnets transformer Gray converter circuit Motor alternator set replaced with 4 300KVA units (1 redundancy) UPS units currently on order Installed by Q4 2004

Storage Choke Current 1MJ, 2H Storage Choke Ex-NINA, manufactured in the 1960’s Ten interleaved primary and secondary windings Choke windings and core: 90 tonnes Total weight (inc. oil): 120 tonnes 30 years of service State of insulation unknown, leaks oil, failure would result in ISIS being down for extended period of time

Replacement chokes Current 2H storage choke 10 off replacement 200mH chokes …X10 1/5 scale models 40mH Minimise financial and technological risk Due September 04 Full scale prototype/spare

Replacement chokes Most probable design is a ‘frame’ type storage choke Energy stored (air gaps) = ½ L I2 Energy stored/unit volume = ½ μ0 B2 Calculate dimension of air gaps For 200mH, 1010A, 100KJ, 0.9T: Volume ~0.3m3 Size and distribution of these critical in controlling losses

Replacement chokes Testing of scale models to take place September 2004 Losses Stray magnetic fields Leakage inductance Linearity Noise (mechanical) Cost

Summary New capacitor banks Installed 2002 New UPS system Installed by Q4 2004 New split choke system Scale model testing Q4 2004 Prototype and production chokes 2005/6